1. Field of the Invention
The invention is in the field of free piston displacer movement by a crankshaft driving means having an offset mass flywheel operably connected to a directional flow control valve and to the displacer piston to respectively control the working fluid pressure waves to the cooler and to maintain a natural frequency of free piston displacer reciprocation.
2. Description of the Prior Art
A free displacer of a split cycle cryogenic cooler usually follows the sinusoidal waveforms of the working fluid pressure applied to the cold end in which the pneumatic volume does little to alter the sinusoidal waveforms. Even though magnetic means have been used to alter these sinusoidal waves into a more square type displacer waveform, i.e. provides dwell time at the extreme ends of displacer movement, the magnetic fields in the metal parts causes undesirable electronic noise. The present invention is comprised of a mechanical means for alternately driving and braking the piston displacer to produce flat top dead center and flat bottom dead center displacer waveforms.